thanks for all your comparisons. They seem to confirm the best that one could reasonably hope from a 5x, reduced image circle zoom lens like the 17-85 EF-S:

a) It is better than its natural 35mm format counterpart, the 28-135 (same 5x zoom range, same angular FOV range), at least when are used with the smaller format.

It is as sharp as the 17-40 L (though with worse CA). Given that the 17-40 has the optical design advantage of a far narrower 2.4x zoom range, and is more expensive despite lacking IS, this sounds like quite a good performance from the 17-85.

Almost all of the time, zooms win with me for the advantages of less lens swapping and/or less of the cropping needed when the best available prime is significanlty shorter than ideal for the composition.

Convenience is a major factor in my purchases, too. But I almost swapped my 50mm f/1.4 (and some money inbetween) today for a 24-70mm f/2.8L, until I suddenly recalled a few shots that would be really icky to take without f/2 or better. I'm still getting that zoom, though, since I'm an equipment freak.

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One other case for primes is at extremes of telephoto such as for wildlife photography. The tendency then is that, prime or zoom, you are going to take a lot of shots at the maximum available focal length wth no flexibility to get perfect framing, so that ther wil often be significant cropping. Then what counts is having the longest, sharpest lens. For that a prime is likely the best choice, and can also save some weight.

Is it only me, or are there others who think there's a hole in the prime lens lineup around 200mm? Sure, there's that chunk of L glass, but there's no IS! I'd really like a 200mm prime with IS. But maybe everybody who wants that just buys the 300mm f/4L IS instead.

The only two lenses I can remember that Canon have brought out recently for 1-series cameras are the 400mm DO and the 70-300DO.

Yes, but Canon hasn't brought out any telephoto primes or zooms for their reduced frame cameras, so BJL's point still stands.

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I suspect part of the reason for a lack of new lenses targeted at the 1-series camera is a desire on Canon's part to perfect the DO technology such that it provides them with a differentiator in the marketplace. As to 200mm on a Canon a prime it would have to be going some to beat the quality of the 70-200 zoom lenses, perhaps having wider apeture would be the differentiator. Now a 200mm/f1.2 DO IS lens at half the weight and size of the zoom may be interesting.

Canon already had a 200mm prime with a quality that was superb, the f/1.8L USM, but they discontinued it. Its weight was 3kg, so it wasn't exactly a light lens, and IS certainly wouldn't have helped in that regard.

But the f/2.8L II USM is apparently also very good (as far as I can recall from statements, a bit sharper than the 70-200mm f/2.8L IS), and weighs "only" 765g. An IS version of this lens would be very interesting, and might weigh in at less than 1kg.

There is one topic we haven't hit upon. That is the extra light being bounced around inside the mirror box/lens by significant overcoverage of the sensor and the fact the sensor itself is hmmmm 'reflective' and throws light back.

I was just about to mention that; Canon has quietly modified some of its telephoto lenses to reduce this problem: changing the rear elements a bit and adding anti-flare coatings I believe. I have also read that the new "digital friendly" DG versions of many Sigma 35mm format lenses currently being rolled out vary mainly in adding such coatings.

About new Canon lenses: there have been several recent Canon EF (35mm format usable) lens introductions: in addition to the 400/4 DO and 75-300 DO, there have been two L lenses, the 28-300 f/3.5-5.6L and 17-40 f/4L.

The 17-40L, and lack of corresponding "EF-S L" lenses, is somewhat noticable as evidence of their reluctance to make high quality lenses for smaller formats only. Its focal lengths seem "1.6x friendly", but they instead made it cover 35mm format as well, gaining ultra-wide coverage when used with 35mm format, but substantially impairing its cost/weight/speed trade-offs when used in 1.6x, compared to what would have been possible with a smaller image circle design. (Compare to the Pentax 16-40 f/4, Olympus 14-54 f/2.8-3.5 or Nikon 18-70 f/3.5-4.5.)

Sorry for interrupting the slumber but I just thought I should add a minor nit-pick: I mostly shoot portraits and art photography of various genders. The point is that time or speed is rarely an issue for me. I used to own 2 lowly Sigmas (18-50mm f/3.5-5.6 & 28-105mm f/2.8-4) to go along with my 20D. Then something happened: I accidentally bought the Canon 50mm f/1.8. All I can say is that I am now addicted to both the “brutal” quality, the lower cost and last but not least the superb feeling of shooting primes. Somehow they give u more time to think and compose better. It is a completely different feeling for me. And I love it. In a few days I will be the proud owner of Canon EF 24mm f/2.8 , Canon EF 50mm f/1.4 USM and Canon EF 100mm f/2.8 USM Macro. These will serve me nicely for ALMOST all of my needs :38mm, 80mm and 160mm. The only concern is that I don’t have the wide angle covered. I wish Canon would come up sooner then later with a EF-S 15mm f/2.8 prime (at a reasonable price) to round up my kit. Do u foresee such a lens in the near future? And no, 10-22 EFS would not satisfy me